Sanding machine



June 17, 1969 T. J. LEVEQUE 3,449,868

sANnING MACHINE Filed sept. 1e, 196e sheet of e n Afro/mns June 17, 19691'. J. LEvEQuE SANDING MACHINE Shet Filed Sept. 16, 1966 www www

INVENTOR. TRE/:FLE J, EVEQUE A T TORNEYS June 17, 1969 1'. J, LEVEQUE3,449,868

SANDING MACHINE Filed Sept. 16, 1966 Sheet 3 0f 6 FIG. 3

, INVENTOR. TREFFLE J. LEVEOUE A T TORNE'YS BY I June 17, 1969 SheetFiled Sept. 16, 1966 5 R. 8N wm w m w: mmm wm No. mwN m wm NU, m N L vmi @Q W wm mm E om mo. m Ill vm lq. A# wo. ww NMQ Nw om om ATTORNEYSJune 17, 1969 1'. J. LEVEQUE SANDING MACHINE 5 ore Sheet Filed Sept. 16.1966 m9 vm- INVENTOR.v TRE/FLE J El/500E Hmm ATTORNEYS sheet 6 of e June17, 1969 12J. LEvEQuE SANDING MACHINE Filed Sept. 16, 1966 United StatesPatent U.S. Cl. 51-141 7 Claims ABSTRACT OF THE DISCLOSURE A portable,bodily manipulatable, power, surface finishing machine having an endlesssurface-finishing belt trained around parallel spaced apart rollers anda motor mounted on a roller support frame and extending laterally fromone side thereof in parallel relation with the rollers in the region ofone roller to which it is drive connected. The motor is disposed inparallel spaced apart relation between two tool-manipulating handleswhich also extend laterally from the aforesaid side of the frame, withthe axis of one handle being disposed rearwardly of the drive roller andthe axis of the other handle extending between the two rollers toprovide a balanced relationship with the motor.

This invention relates to power tools and particularly to improvementsin portable surface-finishing machines of the traveling band type. Thepresent invention is especially concerned with portable Sanders and thelike wherein a surface-finishing belt is trained around spaced apartmotor driven and idler pulleys.

A major object of this invention is to provide an improved portable,power driven surface-finshing machine having a novel compact, balancedarrangement of parts which renders the machine easily manipulatable andespecially adaptable for contour surface finishing work.

The arrangement of parts according to this invention provides acomfortable balance, easy manipulation of the machine, and an unblockedview of the workpiece surface. It also allows the operator to standcomfortably to one side of the machine and to hold his elbows close tohis body for firmly guiding the machine. In addition, no part protrudesappreciably beyond the outboard edge of the belt to thus allow the beltto be guided into confined regions and corners. The machine of thisinvention thus is particularly suitable for finishing automobile bodysurfaces and the like.

A further object of this invention is to provide a belttypesurface-finishing machine with a novel back-up shoe or pressure platenassembly for supportingly engaging the inner surface of the workpieceengaging belt flight and thereby applying a uniform pressure to theeffective working area of the belt. As more specic objects, thisinvention provides for a novel back-up shoe or platen which is quicklyand easily removable and mountable in place, which allows increasedflexibility of the working run of the belt to accommodate unevenworkpiece contours, and which is compactly located together with a quickchange mounting structure between opposed flights of thesurfacefinishing belt.

Yet another object of this invention is to provide a belt-typesurface-finishing machine with a novel drive and idler pulley structureto insure proper tracking of the surface-finishing belt around the driveand idler pulleys and to minimize the belt wear occasioned by engagementof the belt edges with pulley flanges.

Further objects of this invention will appear as the descriptionproceeds in connection with the appended claims and annexed drawingswherein:

FIGURE l is a partially sectioned top plan view of a portable beltsanding machine incorporating the principles of this invention;

3,449,868 Patented June 17, 1969 rice,

FIGURES 2 and 3 respectively are front and rear elevations of thesanding machine shown in FIGURE 1;

FIGURE 4 is a section taken substantially along lines 4 4 of FIGURE 2;

FIGURE 5 is a section taken substantially along lines 5 5 of FIGURE 1;

FIGURE 6 is a section taken substantially along lines 6 6 of FIGURE 5;

FIGURE 7 is a section taken substantially along lines 7 7 of FIGURE 2;

FIGURE 8 is a section taken substantially along lines 8 8 of FIGURE 1;

FIGURE 9 is a perspective view of the pulley support tube shown inFIGURES 1 and 2;

FIGURE 10 is a section taken substantially along lines 10-10 of FIGURE1;

FIGURE 1l is a section taken substantially along lines 11-11 of FIGURE1; and

FIGURE l2 is a section taken substantially along lines 12 12 of FIGURE2.

Referring now to the drawings and more particularly to FIGURES l and 2,the portable, poweroperated sanding machine embodying the principles ofthis invention is shown to comprise a frame 20 which rotatably supportsa power-driven pulley assembly 22 and an idler pulley assembly 24 spacedlaterally forwardly from pulley assembly 22. An endless, sanding belt 26of suitable conventional form is trained around pulley assemblies 22 and24 and has a lower, substantially straight ight for engaging workpiecesto be surface-finished. An electric motor 28 is carried by frame 20 fordriving pulley assembly 22 in a counterclockwise direction to advancethe lower workpiece-engaging belt iiight from left to right as viewedfrom FIGURE 2.

As shown in FIGURES 1-4, motor 28 comprises a housing 30 having ahollow, open-ended cylindrical section 32. An end plate 34 mounted atthe rearward end of section 32 denes a series of axially extending airinlet ports 36 as best shown in FIGURE 3.

As best shown in FIGURES 1 and 4, housing 30 mounts a pair of axiallyaligned, spaced apart anti-friction roller bearing assemblies 38 and 40which journal a rotor shaft 42 extending coaxially through housingsection 32. A rotor 44 mounted on rotor shaft 42 between bearingassemblies 38 and 40 is circumferentially surrounded by a stator 46 andhas a commutator section 48 engaged by carbon brushes 50 (one shown inFIGURE 1). Stator 46 is securely fixed to housing 32 by cap screwsindicated at 52.

As best shown in FIGURES 2 and 4, the forward end of housing section 32is closed by an end plate 53 having a bored boss 54 which receivesbearing 40. The forward end of shaft 42 extends coaxially through boss54 and into a gear compartment 55.

Gear compartment 55, as shown in FIGURES 4 and 5, is delimited by endplate 53 and a gear housing 56. End plate 53 and housing section 32 arerigidly xed to gear housing 56 by machine screws 58.

Referring to FIGURES 4-6, the forward end of shaft 42 is axially splinedat 60 to provide teeth which constantly mesh with a large diameteredgear 62 in compartment 55. Gear 62 is journalled on a shaft 64 byaxially spaced apart bearings 66 and 68 (see FIGURE 6). The rearward endof shaft 64 is press-fitted into a bore 70 formed in end plate 53. Theopposite end of shaft 64 is slidably received in an aligning hole 72bored through gear housing 56.

With continuing reference to FIGURES 4 and 5, gear 62 constantly mesheswith a gear 74 which is non-rotatably mounted on a pulley drive shaft76. The axis of shafts 42, 64, and 76 are parallel. Shaft 64 extendsbelow 3 and to one side of shaft 42, and shaft 76 is vertically belowshaft 42.

Gears 74 and 62, as shown in FIGURES 4 6, are received in compartment 55which is delimited by internal, axially extending, aligned skirtsections 78 and 80 respectively formed integral with gear housing 56 andend plate 53. A gasket 82 clamped 1between opposed end faces of skirtsections 78 and 80 prevent leakages of gear lubricant from compartment55. Gear compartment 55 is completely enclosed by skirt sections 78 and80 and the opposed end wall portions of gear housing 56 and end plate53. Gears `62 and 74 are sized to provide for a suitable speed reductionand form the gear train drivingly connecting shaft 42 to shaft 76.

As best shown in FIGURE 4, gear housing 56 is formed with a forwardlyextending pulley support hub 86 through which shaft 76 coaxially andfreely extends. Shaft 76 is journalled in axially spaced apart ballbearing assemblies 88 and 90 which are coaxially received in hub 86.Bearing assembly 88 is axially confined between an annular radiallyextending hub lip 92 and an annular spacer 94 through which shaft 76rotatably extends. Bearing assembly 90 is axially confined betweenspacer 94 and a groove and a grove-seated retainer ring 96 carried bygear housing 56. The hub of gear 74 is axially confined between bearingassembly 90 and a lock nut 98 threaded onto the rearward end of shaft76.

Pulley assembly 22 is shown in FIGURE 4 to co m prise a rigid, metallichub 100 and a resilient, belt-engaging tire or annulus 102 which is madefrom a suitable elastomeric material and which will be described indetail later on. The forward end of shaft 76 protruding beyond hub 86non-rotatably extends with a press t through a bored boss section 104 ofhub 100. A locking screw 106 is threaded into the outboard end of shaft76.

Still referring to FIGURE 4, hub 100 is formed with an axially extendingsleeve section 106 which is integrally joined to boss section .104 by aradial web portion 108. Sleeve section 106 is formed with a smooth,uniformly diametered periphery and extends axially rearwardly tocircumferentially surround hub 86. Annulus 102 is press-fitted ontosleeve section 106 axially between pulley flanges 110 and 112. Flange110 is mounted on the outboard end of hub 100 by machine screws 114 (seeFIGURE 2). Flange 112 peripherally surrounds sleeve section 106 at theinboard end of hub 100 and is axially confined between the inboard endface of annulus 102 and a radially outwardly turned, annular lip 116formed integral with sleeve section 106. This construction of pulleyassembly 22 provides for easy assembly and disassembly of hub 100,annulus 102, and flanges 110 and 112.

From the pulley, motor, and gear housing construction thus fardescribed, it will be appreciated that pulley assembly 22 is mountedforwardly of gear housing 56 and motor 30 is mounted rearwardly ofhousing 56. The rotor axis of motor 30 is parallel to and verticallyabove the rotational axis of pulley assembly 22 when the sanding machineis held in a horizontal position. Assembly 22 and gear 74 may lbedisassembled as a unit from the unitary sub-assembly of motor 30, endplate 56, gear 62 and shaft 64 by removing screws 58.

As best shown in FIGURES 1 and 2, a frame-mounted bracket .120preferably formed integral with gear housing 56 extends forwardly fromthe front face of housing 56 .and between pulley assemblies 22 and 24.Bracket 120 is integrally formed with a split collar section 122 alongan axis normally intersecting the rotational axis of shaft 76substantially midway between flanges 110 and 112. The rearward end of anidler pulley support tube 124 forming a part of frame 20 is coaxiallyreceived in collar section 122. The split portions of collar section 122are integrally provided with lateral ears 126 and 128. A machine screw130 extending through aligned bores in ears 1 26 and A128 is threadedinto a nut 132 to tightly clamp the rearward end of tube 124 in collarsection 122.

Still referring to FIGURES 1 and 2, bracket 120 is integrally formedwith a fender plate section 134 extending and between pulley assembly 22and collar 122. Fender section 134 comprises a skirt extending thelength of pulley assembly 22 and in close proximity to the beltengagingperiphery of annulus 102 between opposed flights of belt 26 to deflectparticles downwardly and rearwardly.

As shown in FIGURES 1, 2, and 7, tube 124 extends forwardly betweenopopsed flights of belt 26 and supports idler assembly 24 at its forwardend. Idler assembly 24 comprises a pair of aligned, axially `spacedapart roller units and 141 and a biasing plunger .142.

Roller unit 140, as best shown in FIGURE 7, comprises a resilient tireor annulus 144 which is made of suitable elastomeric material such asrubber and which is coaxially mounted on a rigid hub 146. Plunger 142extends between roller units 140 and 141 and has an axially extendingarm portion 148 received in hub 146. An anti-friction roller bearingassembly 150 is mounted on a member 15.1 extending through arm portion148. Bearing assembly 150 supports hub 146 for rotation .about an axisnormally intersecting the longitudinal axis of support tube 124 andaxially aligning with the rotational axis of roller unit 141. Hub 146 ispress-fitted on the outer race of bearing assembly 150. Bearing assem-Ibly 150 is axially retained between a retainer ring 152 and the head ofa machine screw 154 coaxially threaded into the end of member 151.

Roller unit 14.1 is of the same construction as roller unit 140.Accordingly, like reference numerals have been used to identify likeparts. A bearing assembly 156 mounted on member 151 journals roller unit141 for rotation about an axis aligning with roller unit 140. Rollerunits 140 and 141 are axially confined between the head of screw 154 andthe enlarged head of member 151.

From this description, it is clear that roller units 140 and 141 areindependently mounted for rotation on plunger 142. This constructionenables all of the idler frame support parts to be` located laterallyinwardly of a plane containing the outboard edge of belt 26. From FIGURE1 it is apparent that no parts except flange 110 project beyond a planecontaining the end faces of roller unit l141 and the sub-assembly ofannulus 102 and hub 100. This feature enables the sanding machine of thepresent invention to be used effectively in performing contour sandingor other surface-finishing operations as on automobile bodies since belt26 can readily be positioned in confined corners without interferencefrom parts forming the sanding machine assembly.

With continued reference to `FIGURE 7, plunger 142 slidably androtatably extends into support tube 124 and is formed with a flat-sidedplate section 160. The width of plate section 160 extending into supporttube 124 is made sufliciently small to provide a sliding fit thatenables plunger 142 to be rotated about the axis of tube 124 for apurpose to be explained shortly.

A helically coiled spring 164 received in support tube 124 is compressedbetween the rearward end of plunger 142 and a cylindrical plug 166.Spring 164 reacts against plug 166 to bias plunger 142 and idlerassembly 24 forwardly along the axis of tube 124 to tighten belt 26.Plug 166 is urged axially rearwardly by spring 164 into abutment with asplit, groove-seated retainer ring 168 in the rearward end of tube 124.

As shown in FIGURES 1, 2, and 8, a bracket assembly 170 is mounted onthe forward end of support tube 124 for retaining the rotational axis ofidler assembly 24 parallel with the rotational axis of drive pulleyassembly 22 when plunger 142 is urged forwardly by spring 164 to itsbelt tightening position. Bracket assembly 170, as best shown in FIGURE8, comprises a clamping block 172 fixed by machine screws 173 to asupport bracket 174.

Clamping block 172 is formed with a smooth-walled, arcuate groove whichcooperates with the planar top face of bracket 174 to form asemi-circular channel 176. The forward end of support tube 124 isnotched at 178 (see FIGURE 9) and extends coaxially through channel 176.The downwardly facing, forward edges of notch 178 are received inparallel, longitudinally extending, upwardly facing grooves formed inthe top surface of bracket 174. This forward, notched end of supporttube 124 is clamped tightly between block 172 and bracket 174 bytightening screws 173.

With continued reference to FIGURE 8, bracket 174 is formed with afiat-sided, flat-bottomed groove 180 which opens upwardly into channel176. The lower portion of plate section 160 freely extends throughgroove 180 with sufficient clearance on both sides to allow plunger 142to be turned in both directions through limited angular distances aboutthe longitudinal axis of support tube 124.

As shown in FIGURES 7 and 8, plunger 142 is integrally formed withflat-sided, parallel arm portions 1-82 and 184 extending at right anglesfrom the opposite sides of plate section 160 about midway between theupper and lower edges thereof. When plunger 142 is in its forwardlybiased, belt tightening position shown in FIG- URES 7 and 8, theundersides of arm portions 182 and 184 seat against the planar top faceof bracket 174 to prevent angular displacement of plunger 142 in eitherdirection. Abutment of arm portions 182 and 184 against bracket 174retains plate section 160 in a plane normally intersecting therotational axis of pulley assembly 22 to thus maintain the rotationalaxis of idler assembly 24 parallel to that of assembly 22.

In accordance with this invention, arm portion 182 is formed with aflat-sided, laterally outwardly opening notch 186 which cooperates withbracket 174 to provide a twist latch :for releasably retaining plunger142 in a retracted, belt-slackening position. Notch 186 is locatedforwardly of bracket 174 when plunger 142 is in its forwardly biased,belt-tightening position where the undersides of arm portions 182 and184 butt against the top face of bracket 174 to prevent rotation ofplunger 142. Notch 186 is formed with a uniform width that is slightlygreater than the longitudinal length of bracket 174 in the region ofgroove 180. When notch 186 is aligned with bracket 174, therefore,plunger 142 may be turned in a clockwise direction (as viewed fromFIGURE such that the upper edge region of bracket 174 passes throughnotch 186. This displacement of plunger 142 is limited by abutment ofthe lower edge of plate section 160 against the edge of groove 180. Withplunger 142 in its angularly displaced position shown in FIGURE 10, theforwardly facing edge 190 (see FIGURE 7) of notch 186 faces and is urgedby spring 164 into abutment with the rearwardly facing end face ofbracket 174 adjacent groove 180 to axially lock plunger 142 in aretracted, belt-slackening position.

When it is desired to latch plunger 142 in its retracted position, idlerassembly 24 and plunger 142 are unitarily pushed rearwardly against thebias of spring 164 by gripping idler assembler 24 and Vapplying pressurewith the palm of the hand along the portion of lbelt 26 trained aroundroller units 140 and 141. When plunger 142 is rearwardly displaced by asufficient distance to align notch 286 with bracket 174, thesub-assembly of idler assembly 24 and plunger 142 is then turnedslightly in a counterclockwise direction (as seen from FIGURE 8) toposition edge 190 axially opposite the rearwardly facing surface ofbracket 174. The sub-assembly of idler assembly 22 and plunger 142 isnow released, allowing the bias exerted by spring 164 to shoulder edge190 against the rearward end face o-f bracket 174. In this lockedposition, plunger 142 and idler assembly 24 are axially retracted fromtheir forwardly biased positions by a sutlicient distance to slacken andthereby enable the removal of belt 26. Rearwardly facing positioningshoulders 192 are provided on plate section 160 and arm portions 182 and184 to butt against the forward face of bracket assembly when notch 186aligns with bracket 174 in its retracted position.

When it is desired to release plunger 142 from latching engagement withbracket 174, belt 26 is positioned around pulley assemblies 22 and 24and the sub-assembly of idler assembly 24 and plunger 142 is turneduntil edge clears the top face of bracket 174. Plunger 142 is thenreleased, allowing arrn portions 182 and 184 to pass over the top faceof bracket 174 as plunger 142 and idler assembly 24 are urged by spring164 to their forward, belt-tightening positions. It thus will beappreciated that the simplified twist latch of this invention providesfor the ready removal and mounting of belt 26.

In further accordance with this invention, a back-up shoe assembly 200is removably mounted on frame 20 for supporting the lower workpieceengaging run of belt 26.

VAssembly 200, as shown in FIGURE 2, extends between pulley assemblies22 and 24 land comprises a resilient pad 202 seated between a rigidpressure or facing plate 204 and a rigid backing plate 206. Facing plate204 has a flat, smooth surface which engages the inwardly facing surfaceof the lower belt flight. The ends of plate 204 are smoothly curved andupwardly turned to provide rounded corners which do not gouge into thebelt. The side edges of plate 204 are bent upwardly to form alongitudinal channel receiving the lower portion of pad 202. Pad 202 maybe formed from one or more layers of suitable resilient material such aspolyurethane and spaces backing plate 206 vertically above plate 204.The side edges of plate 206 are bent to provide a downwardly facingchannel in which pad 202 is seated.

Plate 204 is separable from pad 202 and is snugly held against thebottom face of the pad by the tension in the lower belt flight. Thisbelt tension urges backing plate 206 into abutment with the bottom faceof bracket 174 and the bottom face of a back-up shoe mounting plate 208.Plate 208 is fixed to collar section 122 by screw 130 and by a furtherscrew 210 (FIGURE 1).

As shown in FIGURES 2 and 10, backing plate 206 is integrally formedwith a raised forwardly extending tonbue 212 which slidably extends intoa rearwardly and sidewardly opening, fiat-sided groove 214. Tongue 212is straight and extends essentially in parallel relation with thelongitudinal axis of tube 124. Groove 214 is formed in bracket 174 andextends horizontally from a region vertically below tube 124 to the sideof bracket 174.

At its inner end, groove 214 is formed with a downwardly opening recess216 located below tube 124 and substantially medially intersected by aplane containing the longitudinally axis of tube 124. Tongue 212 isurbed upwardly to seat in recess 216 by the tension in the lower beltflight. The flights of belt 26, as previously mentioned, are tensionedas a result of the bias exerted by spring 164.

As shown in FIGURES 2 and 11, backing plate 206 is integrally formedwith a second rigid tongue 220 which is parallel to, but extends in theopposite direction from tongue 212. Tongue 220 extends into a forwardlyand upwardly opening groove 222 formed in plate 208. When belt 26 isadvanced, the frictional engagement between the lower belt flight andbacg-up shoe assembly 200 urbes tongue 220 to a position of maximumprojection into groove 222. Engagement of tongues 212 and 220 with theside edges of recess 216 and groove 222 respectively prevents lateraldisplacement of back-up shoe assembly 200 relative to belt 26.

Back-up shoe assembly 200 is quicgly and easily removed simply bypressing the forward end downwardly to a position where tongue 212clears recess 216 and then by swinging the forward end of the assemblyin a direction to move tongue 212 out through the side opening of groove214. Assembly 200 readily pivots about an axis passing throubh tongue200 at right angles to the axis of tube 124, thereby enabling tongue 212to easily be slid out of groove 214. After tongue 212 is removed fromgroove 214, assembly 200 is shifted forwardly to remove tongue 220 fromgroove 222. When assembly 200 is mounted on frame 20 tongue 220 is firstinserted into groove 222 and tongue 212 is then inserted sidewardly intogroove 214. The tension in the lower belt flight snaps tongue 214 intorecess 216.

Removal and insertion of assembly 200 is more easily facilitated byfirst latching the sub-assembly of idler 24 and plunger 142 in itsretracted position to loosen belt 26. This quicg-change feature providesfor the quick and ready replacement of back-up shoes of varying shapesto obtain access to surfaces of different contours.

In accordance with this invention, pad 202 is compressible to allowlimited rocking movement of facing plate 204 about an axis extendingparallel to and vertically below the axis of tube 124. This rockinglmotion provides the lower belt flight with sufcient flexibility toyallow it to follow and engage uneven workpiece contours. Plate 204 thuseffectively floats on the cushion provided by pad 202 to assure a moreuniformly finished surface.

Advantageously, a covering 223 (see FIGURES and 11) is adhered to thebottom face of par 202. Covering 223 may be made from any suitablematerial which preferably is similar to the surface-finishing beltmaterial. With this construction, facing ylate 204 may optionally beremoved to allow covering 223 to seat against the inside surface of thelower belt flight. This provides the lower belt flight with greaterflexibility.

As shown in FIGURES 1 and 2, a forward, tool manipulating handle 226 isfixed by a machine screw 228 to an upstanding ear of a mounting bracket230. Bracket 230 is removably iixed to tube 124 by a clamping plate 232and two bolt and nut assemblies 234.

Handle 226 has a cylindrically elongated gripping section 236 extendingalong an axis that is substantially at right angles to a planecontaining the inboard side edge of belt 26. Gripping section 236 islaterally offset from belt 26 on the same side as motor 28 and isessentially parallel with the rotational axis of motor shaft 42. Handle226 is disposed forwardly of motor 28 and extends along an axis thatpasses above the top iiight of belt 26. The axis of gripping section 236is contained in a plane normally intersecting the axis of tube 124 aboutmidway between pulley assemblies 22 and 24.

Still referring to FIGURES l and 2, a second tool manipulating handle238 is mounted on an extension 240 forming a part of end plate 53 andextending laterally from motor 30 to a region that is hearwardly ofpulley assembly 22. Handle 238 has a cylindrically elongated grippingsection 242 which is substantially coextensive and parallel withgripping section 236. Gripping section 242 thus extends parallel withmotor 28 and is disposed rearwardly of pulley assembly 22. Motor 28 isthus positioned between handles 226 and 238. The longitudinal axes ofgripping sections 236 and 242 are contained in a plane which issubstantially parallel with the opposed runs of belt 26.

With the foregoing arrangement of handles 226 and 238 relative to motor28 and the other parts of the sanding machine, the operator is able tostand to one side of the machine, gripying handles 226 and 238 in thepalms of his hands. Handles 226 and 238 are spaced sufficiently close toenable the operator to position his elbows close to his body whenholding the sanding machine about waist high in front of him.

By locating motor 28 laterally to one side of belt 26, the overallcenter of gravity of the sanding machine is located between handles 226and 238 since motor 30 represents the heaviest component of the machine.Handles 226 and 238 are so spaced on opposite sides of motor 28 as tobalance the weight to be carried at each handle. This unique arrangementof parts thus provides for a wellbalanced portable tool that is easilyand comfortably manipulatable.

In further accordance with this invention, a fan 246 (see FIGURE l) isnon-rotatably mounted on the forward end of rotor shaft 42 in closeradial alignment with circumferentially spaced apart air discharge ports248. Ports 248 are defined by rearward opening recesses in end plate 53and the opposing, forward end of motor housing section 32.

When motor 28 is energized, fan 246 draws air into housing 30 through-ports 36 at the rearward end of motor 28. This air is drawn axiallyover the rotor and stator surfaces and the rotor shaft bearings and isdischarged by fan 246 radially through ports 248 to form a protectiveair screen when it is essentially parallel to the plane containing theinboard side edge of belt 26 and which normally intersects the forwardends of handles 226 and 238.

Owing to the arrangement of handles 226 and 238 with the other parts ofthe sanding machine, the air screen provided by fan 246 extends betweenthe operators face and belt 26. This air screen thus makes use of theexhausted motor Ventilating air to deflect dust and chips away from theoperators face.

In further accordance with this invention a switch actuator 250 forcontrolling the operation of motor 28 is shown in FIGURES 1 and 12 to bemounted at the inner end of handle 238 so that the operator canconveniently shift it between on and off positions with his thumb whilegrasping handle 238 in the palm of his hand. Actuator 250 comprises acollar 252 which is rotatably mounted on a short sleeve 254. Sleeve 254is coaxially threaded onto a nipple 255 which is threaded into a tappedbore formed through extension 240. The outer end of nipple 255 isthreaded into the inner end of handle 238 to thus x handle 238 toextension 240.

A thumb engaging projection 256 (see FIGURES 1 and 2) formed integralwith collar 254 extends radially beyond the inner end of handle 238which is flanged at 258. Also formed integral with collar 254 are a pairof parallel, spaced apart, axial lfingers 259 and 260 which, as shown inFIGURE 5, extend through an arcuate slot 261 in extension 240.

With continued reference to FIGURE 5, fingers 259 and 260 extend onopposite sides of a switch operating stem 264 which forms a part of aconventional toggle switch 266. Switch 266 is received in gear housing56 and is fixed between opposed faces of extension 240 and gear housing56. The output terminals of switch 266 are connected by leads 268 tostator 46. The input terminals of switch 266 are connected to sheathcovered electrical conductors 270 which extend through nipple 255 andthrough handle 238, the interior of which is hollowed out as indicatedat 272 in FIGURE l2.

By engaging projection 256 with his thumb, the operator can rotateactuator 250 in opposite directions to alternatively engage fingers 259and 260 with stem 264, thereby tripping stem 264 between its on and offpositions. Projection 256 advantageously terminates in a pointer 273(FIGURE 1) which cooperates with markings on extension 240 to indicatewhether switch 266 is in its on position or its olf position. Agroove-seated, O- ring 274 (FIGURE 12) carried by collar 252 is axiallycompressed against the inner flanged end of handle 238 to provide anannular seal for preventing dirt and other foreign particles fromentering the housing space in which switch 266 is mounted.

In the manufacture of the sanding machine of this invention, pulleyassemblies 22 and 24 are accurately assembled on frame 20 yby using asuitable jig to assure that the drive and idler pulley rotational axesare closely parallel. Close parallelism 0f the pulley axes improves thetracking of belt 26 around the pulley assemblies to minimize sidewardbelt movement and consequential, objectionable, wear producingengagement of the belt edges with pulley flanges and 112.

Despite accurate yassembly of the sanding machine parts, however, thepulley rotational axes usually are not perfectly parallel owing tounavoidable manufacturing tolerances. This non-parallelism, which wouldnormally result in some sideward movement of belt 26, is compensated forby the special construction of tires 102 and 144 which will now ybedescribed.

As best shown in FIGURE 4, tire 102 is integrally formed with a seriesof radially outwardly extending, parallel spaced apart, flexible ribs280 of uniform diameter. Ribs 280 are disposed in side-by-side relationcircumferentially around the pulley body.

With continuing reference to FIGURE 4, ribs 280 define a series ofcircumferential, radially outwardly opening, flat-sided grooves 282 ofuniform depth and width. The depth of grooves 282 is shown to be greaterthan the tickness of ribs 280, and the axial spacing between adjacentribs is made sufficiently large such that one rib does not objectionablyinterfere with the other if it is flexed.

When motor 28 is energized to advance belt 26, flanges 110 and 112 limitsideward movement of belt 26. This sideward movement may be the resultof a side thrust applied by the operator in moving the belt laterallyover the workpiece surface. It also may be the result of an inherentnon-parallelism between the rotational axes of pulley assemblies 22 and24, manufacturing imperfections in the surface-finishing belt, or beltdistortion.

The construction of ribs 280 is such that they will be flexed laterallyby a very small distance from planes normally intersecting the pulleyrotational axis when belt 26 is moved laterally towards either of thepulley flanges. Ribs 280 provide no more than a negligible reactionsurface against which a side thrust can act to drive belt 26 intoengagement with either flange 110 or flange 112. As a result, the actionforce tending to drive belt 26 into engagement with either of the pulleyflanges will also be negligible since it cannot exceed the magnitude ofthe reaction force. Without a solid reaction surface, belt 26effectively floats on ribs 280.

By minimizing the magnitude of the belt side thrust in this manner, wearof the belt edges by engagement with llanges 110 and 112 is minimized.It thus will be appreciated that instead of utilizing an opposing forceto keep belt 26 centered, this invention substantially eliminates theaction force or side thrust by reducing the reaction force at ribs 280to a negligible magnitude. In this manner, the inherent manufacturingimperfections of the sanding machine are compensated for to insurecorrect tracking of the belt around the pulley assemblies.

The idler tires 144, as shown in FIGURES 1 and 7, are provided with arib and groove construction which is the same as that just described fortire 102. Accordingly, like reference numerals have been used todesignate the ribs and grooves. The function of the rib and grooveconstruction of tires 144 is the same as that explained for tire 102.

Referring back to FIGURE 4, it will be noted that circumferential,radially outwardly opening grooves 286 are formed between the endmostones of the drive pulley ribs 280 and the opposed faces of flanges 110and 112. Grooves 286 provide spaces to allow the endmost ribs 280 toflex toward flanges 110 and 112. Grooves 286 also prevent the edges ofbelt 26 from becoming wedged between the endmost pulley tire ribs andthe opposed faces of flanges 110 and 112.

The diameters of flanges 110 and 112 are sufficiently large to preventbelt 26 from climbing over the flanges. These flange diameters, however,are not made so large that they are likely to engage and mark theworkpiece surface.

As shown in FIGURES l and 7, pulley assembly 24 is flangeless, and thetwo outermost tire ribs 288 of assembly 24 are smaller in diameter thanthe remaining tire ribs which are uniformly diametered. This novelconstruction keeps belt 26 from becoming lodged between the adjacentoutermost pair of ribs and from jumping ribs 288 when a side thrust isexerted. It was found that when ribs 288 were formed with the samediameter as the remaining tire ribs, belt 26 would tend to become lodgedbehind either of the outermost ribs and then jump the outermost rib asthough it were a flange when sideward pressure was exerted on the belt.When the side pressure ceased, the belt would jump back, thus moving inan erratic path. In addition to eliminating this objectionablecondition, the reduced diameter of ribs 288 effectively provides pulleyassembly 24 with a crowned configuration owing to the tendency of thetire ribs to deform. The crown in idler assembly 24 further minimizessideward movement of belt 26.

Advantageously, a belt guard 290 may be removably mounted on frameassembly 20. Guard 290 is disposed above and parallel with the upperbelt flight. The rearward end of guard 290 is curved to extend partiallyaround pulley assembly 22. The forward end of guard 290 is detachablyfixed to frame 20 by a bracket and machine screw assembly 292. Therearward end of guard 290 is secured to gear housing 56 by a machinescrew 294.

Referring back to FIGURE 2, back-up shoe assembly 200 may be reversiblymounted on frame 20 since tongues 212 and 220 are substantially of thesame configuration, each being insertable into either groove 214 orgroove 222. Thus, assembly 200 may be turned degrees and mounted inplace by inserting tongues 212 and 220 respectively into grooves 222 and214. The advantage of this reversible back-up shoe construction is thatthe forward and rearward ends of plate 204 may be provided Withdifferent configurations for alternate use simply by reversing theposition of assembly 200. In the position of assembly 200 shown inFIGURE 2, the forward upturned end of plate 204 adjacent to pulleyassembly 24 is provided with a more gradual and more elongated curvaturethan the rearward end thereof. Thus, a more gradually inclined workpiecesurface may be finished uniformly. If the workpiece surface is socontoured that a shorter, upwardly curved pressure plate end is neededto obtain a uniform finish, the operator simply reverses backup shoeassembly 20.0 to place the presently shown rearward end adjacent topulley assembly 24.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A portable, bodily manipulatable power tool for surface-finishingworkpieces comprising:

(a) a pair of spaced apart rollers,

(b) a surface-finishing belt trained around said rollers.

(c) a rigid, elongated support structure extending longitudinallybetween opposed runs of said belt and rotatably mounting said rollers,

(d) a pair of tool-manipulating handles mounted on said supportstructure along longitudinal, essentially parallel axes transverselyintersecting a plane containing one side edge of said belt, the axes ofsaid handles being essentially parallel with the rotational axes of saidrollers,

(e) a motor having a housing and a drive shaft rotatably Isupported insaid housing about an axis extending essentially parallel to thelongitudinal handle axes and laterally from said plane at the region ofone of said rollers,

(f) means drive connecting said shaft to said one roller, and

(g) means on said support structure for supporting said motor laterallybetween said handles in spaced apart relation thereto,

(h) said handles being disposed rearwardly and forwardly of said oneroller in balancing arrangement with said motor and having grippingsections laterally offset from the side of said plane facing away fromsaid belt.

2. The portable, bodily manipulatable power tool defined in claim 1wherein the longitudinal axis of the forward one of said handles extendsbetween said rollers.

3. The portable, bodily manipulatable power tool defined in claim 1wherein the other of said rollers comprises a pair of axially adjacent,separately formed roller sections, and wherein said support structurecomprises a part extending between said roller sections, and means onsaid part for journalling said roller sections axially inwardly of theopposite side faces of said other roller.

4. The portable, bodily manipulatable power tool defined in claim 1comprising a driven shaft mounting said one roller, means journallingsaid driven shaft on said support structure, and a gear train forming apart of said drive connecting means and connecting said drive shaft tosaid driven shaft, said means supporting said motor comprising a gearhousing mounting said gear train at the end of said motor adjacent saidbelt, means fixing said motor housing on said gear housing, and meansmounting said gear housing on said support structure.

5. A power driven tool for surface-finishing workpieces comprising:

(a) a frame,

(b) a pair of spaced apart roller assemblies carried by said frame,

(c) an endless surfacedinishing belt trained around said rollerassemblies and having opposed runs extending between said assemblies,

(d) a back-up shoe disposed between said runs and supporting theworkpiece engaging run of said belt, and

(e) means reversibly, removably mounting said backup shoe on said frame,

(f) said back-up shoe comprising a rigid pressure plate seated againstthe inwardly facing surface of said workpiece-engaging run and havingbelt engaging ends which are forwardly and rearwardly disposed relativeto the movement of said workpiece engaging run and which are bent towardthe other run of said belt at different curvatures to provide for thealteration of belt contour in the region Where the belt engages theforwardly disposed one of said ends upon reversing the position of saidshoe, whereby alternate belt contours conforming to differentlycontoured workpiece surfaces are provided in the region of saidforwardly disposed end by reversing the position of said shoe.

6. The portable, bodily manipulatable power tool defined in claim 1wherein a plane containing the longitudinal axes of said handles passtransversely through said housing.

7. The portable, bodily manipulatable power tool defined in claim 1wherein axially directed projections of the end surfaces of said oneroller and said motor facing toward each other are in overlappingrelation.

References Cited UNITED STATES PATENTS 1,773,077 8/ 1930 Newman.1,826,177 10/1931 Johnson 5l-170.4 1,913,503 6/1933 Myers 51--l70.42,815,613 12/1957 Van Sittert 51-135 3,334,447 8/1967 Leveque 51-141FOREIGN PATENTS 535,506 4/1941 Great Britain.

JAMES L. JONES, IR., Primary Examiner.

U.S. C1. X.R. 51-170

